Process of vulcanizing plastics.



UNITED sTAT s PATENT oF ro cnnsm J: RANDALL, or NAUGATUC-K, CONNECTICUT,ASSIGNOB To nos'ron RUBBER SHOE COMPANY, A CORPORATION or.MassA'cHUsETTs.

PBOCESS F VULCANIZING PLASTICS.

No Drawing.-

To all whom it may concern: I Be it known that I, CHESTER J. 'RANDALL, acitizen of the United States, and a resident of Naugatuck, county of NewHaven, and State of Connecticut, have invented certain new and usefulImprovements in the Process of Vulcanizing Plastics, of which thefollowing is a full, clear, and exact description. This inventionrelates to processes for vulcanizing plastics and is more particu larlydirected to a process for vulcanizing plastics .which are apt to blowduring vulcanization.

It is well known in.the rubber industry that his impossible to finishthe cure of certain rubber compounds, such as for instancea mixturelacking an active mineral curing agent for example a compound known inthe trade as white stock, with out the use of wet steam in contactthere- 'with. However, even with the use of steam in contact with thearticles formed of the white-sto'ckfl such as for instance soles foroots and shoes, the vulcanized producthas hitherto been imperfect due toblowing or the formation of chambers, cells, or the like in the rubber.This blowing is caused principally because steam at the temperaturenecessary for eflicient vulcanization has in suflicient pressure torestrain the rubber from inflating under the pressure of. the gases,m.fluids, and the like entrapped in the rubber which expand, if notprevented, under the influence of heat. y

a Experiment has proved that a pressure of 60 lbs; is necessary duringthe initial stages of curing whitegrubber articles to prevent blowing;Saturated steam at 60 pounds 40 pressure is too hot for vulcanizing suchmaterial and since the temperature 0 saturated steam for a givenpressure is substantially a constant the pressure may not be reducedwhile maintaining the temperature constant. The temperature of air onthe other hand for a given pressure is a variable and air may be broughtto any desired tempera-' ture for vulcanization at a required pressure.However, it is common knowledge that the cure of white rubber containingarticles cannot be finished by heated -compressed air although the airmay be used during the initial stages of the cure with satisfactoryresults. a With the above in mind the present em- Specification ofLetters Patent.

Application filed May 13 1915. Serial No. 27,749.

Patented Jan. 30,1917.

bodiment of my invention consists inlsuh-i ecting the vulcanizablewhite, rubbefi soles to air at a vulcanizing temperature and under-6Olbsipressure vuntil tlie,soles. have reached a desired degree ofvulcanization, and subsequently subjecting the soles gitoi steam undervulcanizing temperature and 30 lbs pressure tqcomplete the cure, theiinterim between the change from airto steam being utilized in cooling thehot soles while simultaneously maintainin 4 a sufiicientpre's' sure tokeep them from b owing under, the

cooling or reduced temperature. :Bma'd'ly I subject the vulcanizableplastic in a closed chamber to a heat medium atavulcanizing temperatureunder pressure-, unti-l lt he sired vulcanization is effected, marte dmit into said chamber ag'cQO1in gwmd!ufii which makes contact with thehot rubben while the latter is under-the influence'o fan externalpressure. In carrying out the embodiment o my invention in connectionwith the-vulcanization of soles formed 1 of fjwhitemubbefl, stock, thatis rubberlaekingan aetiveQminQ- eral curing agent, the solesaref incl sa vulcanizer andnairsat' atmospheric perature and at '60 lbs; press Jisfi duced into the vulcanizen, Th s compressed air is heated by means ofthe usual steam g5 coils in the vulcanizer, fQ1[;&- -.p1 1Qd]Qf aboutone-half hour until-it atti ns the lo ing temperature of abo it;:27tained at approximately th- ..l for about one-hal fcliourz 0 .5113 hasreached a desiredidegre o vulc tion, that is, is partially hurhdggfllhe, is then opened for the exit of the compresse air and coldair-or air at atmospheric temperature is blown through the vulcanizer incontact with the soles at substantially the blast from 27 0 to 250 F.,or falls about 20.; 1015 The 60 lbs. pressure of the air during thiscooling step positively holds the soles against blowing, that holds therubbenagainst' yielding under the pressure ofthe' entrappedgases,fluids, and the like, the pressure of such gases, fluids, and the likeof course dropplng with the drop in temperature so that at the end ofthe ten minuteperiod in which the air blast is employed the pressure ofsuch, entrapped gases, fluids, and the like willbe so reduced that thepressure of the air blast may be reduced considerably without danger ofthe rubber blowing. Moreover, cooling the stock so stifl'ens it as toenable it to withstand'considerable internal pressure. 'At the end ofthe ten minute period above referred to, the pressure of the air blastis reduced fro'mfiO lbs. to lbs. and

now steam under a; pressure of 30 lbs. and

under a temperatii-i'e suflicient to complete the vulcanizationlsintroduced into the vulcanizer and maintamedpreferably from 10 to 20minutes or for a period sufiicient to able plastic, including guttapercha, balata,

and the like, which although not commonly vulcanized are capable ofvulcanization or setting;

' Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. The process of vulcanizing rubber or similar material whichcomprises, partialflliy vulcanizing the rubberunder a pressure su cient'to prevent blowing of the rubber, cooling the rubber while maintaininrubber, and completing the'vulcanization under steam at a pressure lessthan that duringpartial vulcanization.

2. The process of vulcanizing rubber or similar material whichcomprises, partially vulcanizing-the iubber in contact with a 'fluidvulcanizing medium under a pressure sufiicient to preventblowirsllgi-i-i cooling the rubber under fluid pressure it ata pressuresuificient to prevent blowl gof the approximately 60 lbs. pressure,-cooling cient to pre.

vent blowing of the rubber, and completing the vulcanizationunder steamat a pressure less than that during partial vulcanization.

.3.- The process ,of vulcanizing rubber or similar material whichcomprises, partially ing vulcanization under steam at a vulcanizingtemperature. r

5. The process of treating vulcanizable rubber stock consisting ofpartially curing the stock in contact with air at a vulcanizingtemperature and pressure, cooling the partially vulcanized stock undersuflicient pressure to prevent blowing of the stock while cooling, andcompleting the cure of the stock in contact with wet m at a vulcanizingtemperature and pm p 6. The process of rubber or similar materialnomads, partially vulcanizing the rubber in uni-d. with air at aproximately lbs. cooling the ru ber under air at appmximtely 60 lbs.

pressure, and completing flue vulcanization of the rubber under steam ata lower pressure than that during 7. The processof vulcanizing rubber orsimilar material which comprises, partially vulcanizing the rubber incontact airflat e rubber under approximately 60 lbs. p and completingthe vulcanization of the rubher under steam at approximately 30 lbs.

pressure. 7

Signed at Naugatuck, county of "New Haven, State of Conn., this 11th dayof May,

CHESTER J. RANDALL.

partial vulcanization.

